Study on the preparation of LiMn1-xFexPO4/C from pyrolusite based on first-principles and its electrochemical properties

In this paper, manganese is used as a medium to connect pyrolusite with lithium-ion batteries, which not only meets the needs of comprehensive utilization of global strategic mineral resources, but also maximizes the performance of lithium-ion batteries under the goal of global carbon neutralization and carbon peak. Firstly, the optimum experimental conditions for sulfuric acid roasting of pyrolusite were investigated by single factor experiment and orthogonal experiment: the roasting temperature was 650 °C, the roasting time was 4 h, the acid-to-ore ratio was 2:1, and the water-to-ore ratio was 0.6:1. The roasting temperature plays a major role. Then, LMFxP-C (x = 0, 1/4, 1/8, 1/12, 1/24) cathode materials were prepared by adding different mass Fe elements with manganese element purified from pyrolusite as manganese source. Its electrochemical analysis was carried out: the capacity retention rate of LMF1/4P–C cathode material is 92.54% after 500 cycles. After a total of 150 times of rate tests at different rates, the discharge specific capacity of LMF1/4P–C can still reach 148.5 mAh g−1. At the same time, the EIS results show that the values of Re and Rct of LMF1/4P–C cathode material are the smallest compared with other materials. Finally, the LMFxP-C cathode material was analyzed by first-principles, and the optimal Fe doping amount was theoretically predicted. The crystal structure, bonding and density of states of the LMFxP-C cathode material were calculated and discussed. The results show that when the Fe doping amount is 1/4, the LMFxP-C system has the highest conductivity and the best electrochemical performance. The calculation results are consistent with the experimental results.